PHP fgets Function

last modified April 3, 2025

The PHP fgets function reads a line from a file pointer. It's commonly used for reading files line by line in PHP applications.

Basic Definition

The fgets function reads up to length - 1 bytes from the file pointer. Reading stops when length - 1 bytes have been read, or a newline.

Syntax: fgets(resource $stream, ?int $length = null): string|false. The function returns the read string or false on failure.

Basic fgets Example

This shows the simplest usage of fgets to read a file line by line.

basic_fgets.php

<?php

declare(strict_types=1);

$file = fopen("example.txt", "r");

if ($file) {
    while (($line = fgets($file)) !== false) {
        echo $line;
    }
    fclose($file);
}

This opens "example.txt" and reads it line by line until EOF. Each line includes the newline character at the end. Always close files with fclose.

Reading Specific Length

The second parameter limits how many bytes to read from the line.

fgets_length.php

<?php

declare(strict_types=1);

$file = fopen("example.txt", "r");

if ($file) {
    $line = fgets($file, 10);
    echo $line;
    fclose($file);
}

This reads at most 9 bytes (10 - 1) from the first line. If the line is shorter, it stops at the newline. The length parameter is optional.

Reading CSV File

fgets can be combined with str_getcsv to parse CSV.

csv_reader.php

<?php

declare(strict_types=1);

$file = fopen("data.csv", "r");

if ($file) {
    while (($line = fgets($file)) !== false) {
        $fields = str_getcsv($line);
        print_r($fields);
    }
    fclose($file);
}

This reads a CSV file line by line and parses each line into an array of fields. The newline from fgets is handled by str_getcsv.

Error Handling

Proper error handling is important when working with file operations.

error_handling.php

<?php

declare(strict_types=1);

$filename = "nonexistent.txt";
$file = @fopen($filename, "r");

if ($file === false) {
    echo "Failed to open file: $filename";
    exit(1);
}

while (($line = fgets($file)) !== false) {
    echo $line;
}

fclose($file);

This shows proper error handling when opening files. The @ suppresses warnings, allowing custom error handling. Always check for false returns.

Reading Remote File

fgets can read from remote files when allow_url_fopen is enabled.

remote_file.php

<?php

declare(strict_types=1);

$url = "https://example.com/data.txt";
$file = fopen($url, "r");

if ($file) {
    while (($line = fgets($file)) !== false) {
        echo htmlspecialchars($line);
    }
    fclose($file);
}

This reads a remote file line by line. Note that htmlspecialchars protects against XSS when outputting remote content. Check PHP configuration.

Best Practices

Resource Management: Always close files with fclose.
Error Handling: Check for false returns from file operations.
Memory Efficiency: Use fgets for large files.
Security: Validate/sanitize file paths and content.
Performance: Consider buffering for frequent small reads.

Source

PHP fgets Documentation

This tutorial covered the PHP fgets function with practical examples showing its usage in different file reading scenarios.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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